Methods and apparatus for free-shape cutting of flexible thin glass

ABSTRACT

Methods and apparatus provide for supporting a source glass sheet and defining an at least partially non-straight cutting line that establishes a closed pattern that circumscribes a desired final shape; scoring the glass sheet at an initiation line using a mechanical scoring device; applying a laser beam to the glass sheet starting at the initiation line and continuously moving the laser beam relative to the glass sheet along the cutting line to elevate a temperature of the glass sheet at the cutting line to a substantially consistent temperature, where the laser beam is of a circular shape; and applying a cooling fluid simultaneously with the application of the laser beam, such that the cooling fluid at least reduces the temperature of the glass sheet in order to propagate a fracture in the glass sheet along the cutting line.

This application claims the benefit of priority under U.S.C. §119 ofU.S. Provisional Application Ser. No. 61/925,308, filed on Jan. 9, 2014,the content of which is relied upon and incorporated herein by referencein its entirety.

BACKGROUND

The present disclosure relates to methods and apparatus for fabricatingflexible thin glass into free-form shapes.

Conventional manufacturing techniques for cutting flexible plasticsubstrates have been developed, where the plastic substrates employ aplastic base material laminated with one or more polymer films. Theselaminated structures are commonly used in flexible packaging associatedwith photovoltaic (PV) devices, organic light emitting diodes (OLED),liquid crystal displays (LCD) and patterned thin film transistor (TFT)electronics, mostly because of their relatively low cost anddemonstrably reliable performance.

Although the aforementioned flexible plastic substrates have come intowide use, they nevertheless exhibit poor characteristics in connectionwith at least providing a moisture barrier and providing very thinstructures (indeed, the structures are relatively thick owing to theproperties of plastic materials).

Accordingly, there are needs in the art for new methods and apparatusfor fabricating a flexible substrate for use in, for example, PVdevices, OLED devices, LCDs, TFT electronics, etc., particularly wherethe substrate is to provide a moisture barrier and the substrate is tobe formed into a free-form shape.

SUMMARY

The present disclosure relates to employing a relatively thin, flexible,glass sheet (on the order of less than about 0.3 mm) and cutting theglass sheet into a free form shape.

Flexible glass substrates offer several technical advantages over theexisting flexible plastic substrate in use today. One technicaladvantage is the ability of the glass substrate to serve as goodmoisture or gas barrier, which is a primary degradation mechanism inoutdoor applications of electronic devices. Another advantage is thepotential for the flexible glass substrate to reduce the overall packagesize (thickness) and weight of a final product through the reduction orelimination of one or more package substrate layers. As the demand forthinner, flexible substrates (on the order of less than about 0.3 mmthick) increases in the electronic display industry, manufacturers arefacing a number of challenges for providing suitable flexiblesubstrates.

Although techniques exist for the continuous cutting of ultra-thin glassweb, for example glass web measuring less than about 0.3 mm thick, suchtechniques are directed to cutting the glass web into straight strips ofparticular widths. Conventional approaches for cutting the glass web,however, have not provided for the ability to cut arbitrarily free formshapes.

A significant challenge in fabricating flexible glass substrate for PVdevices, OLED devices, LCDs, TFT electronics, etc., is cutting a sourceof relatively large, thin glass sheet into smaller discrete substratesof various dimensions and shapes with tight dimensional tolerances, goodedge quality, and high edge strength. Indeed, a desired manufacturingrequirement is to cut glass parts off a source glass sheet continuously,without interruption of the cutting line, where the cutting lineincludes at least some round sections (e.g., for rounded corners),possibly of varying radii. Although existing mechanical techniques forcontinuous cutting of irregular (free form) shapes provide for scoring(with a score wheel) and mechanical breaking (or snapping), the edgequality and strength achieved by such mechanical techniques are notsufficient for many applications where precision is required. Indeed,the mechanical scoring and breaking approach generates glass particlesand manufacturing failures, which decreases the process yield andincreases manufacturing cycle time.

In accordance with one or more embodiments herein, a laser cuttingtechnique is employed to cut a thin glass sheet into a free form shape.Glass cutting techniques using a laser are known, however, suchtechniques are directed to cutting glass sheets having thicknesses of atleast 0.4 mm and thicker—and the technique involves laser scoringfollowed by mechanical breaking (score and snap). The cutting of thinflexible glass with thicknesses of less than about 0.3 mm presentssignificant challenges, especially when tight dimensional tolerances andhigh edge strength are required manufacturing objectives. Theconventional laser score and mechanical break process is nearlyimpossible to reliably employ with glass sheet thicknesses of less thanabout 0.3 mm, and especially of less than about 0.2 mm. Indeed, due tothe relatively thin profile of a glass sheet of less than about 0.3 mm,the stiffness of the sheet is very low (i.e., the sheet is flexible),and the laser score and snap cutting process is easily adverselyaffected by thermal buckling, mechanical deformation, air flows,internal stress, glass warpage, and many other factors.

In contrast, the embodiments herein present laser cutting techniquesresulting in free form shapes of thin flexible glass, whereby a one-stepfull separation of the free form shape from the source glass sheet isachieved along virtually any trajectory, including closed contours. Acontinuous cutting trajectory may be established using a combination ofany number of cutting lines having radii of curvature from a minimum ofabout 2 mm up to infinity (which is a straight line).

The novel methodology and apparatus provides for the propagation of acrack in the source glass sheet via a laser (for example a CO2 laserbeam) and simultaneous provision of a cooling fluid (for example a gas,for example air). Initiation of the crack is achieved using a mechanicaltool, preferably outside a perimeter of the desired cutting line. Themethodology and apparatus is applicable to thin and ultra-thin glasssheets with thicknesses of less than about 0.3 mm, for example betweenabout 0.03 mm to 0.3 mm, and/or between about 0.05 mm to 0.2 mm.Notably, cutting of thinner glass sheets is possible, and the cutting ofthicker glass sheets (i.e., greater than about 0.3 mm) is also possible.Although the methodology is intended for a one step, full separation ofthe desired shape from a source glass sheet of less than about 0.3 mm,the technique may be adapted for cutting shaped parts from a glass sheetof thickness of greater than about 0.3 mm, using a score and breaktechnique.

Advantages of the embodiments herein include: (i) producing free formglass shapes from thin and ultra-thin glass sheets with high edgequality and precision; (ii) the flexibility to cut various shapes andsizes; (iii) permitting a cut having a minimum radius of curvature ofabout 2 mm; (iv) reproducible and effective crack initiation and cracktermination; (v) high edge strength and clean cutting process; (vi) verysimple and low cost beam shaping optics, beam delivery optics, and powerlaser source; (vii) application to a wide range of glass thicknesses(including ultra-thin glass sheets).

Other aspects, features, and advantages will be apparent to one skilledin the art from the description herein taken in conjunction with theaccompanying drawings.

DESCRIPTION OF THE DRAWINGS

For the purposes of illustration, there are forms shown in the drawingsthat are presently preferred, it being understood, however, that theembodiments disclosed and described herein are not limited to theprecise arrangements and instrumentalities shown.

FIG. 1 is top view of a thin, glass substrate produced using one or morecutting methodologies and apparatus disclosed herein;

FIG. 2 is a top view of a source glass sheet from which the glasssubstrate of FIG. 1 may be produced;

FIG. 3 is a schematic illustration of an apparatus that may be used tocut the glass substrate from the glass sheet;

FIG. 4 is a graphical representation of speed and power curves versustime (or distance along the cutting contour from the starting point)suitable for use in connection with employing the apparatus of FIG. 3 tocut the glass substrate from the glass sheet;

FIG. 5 is a schematic side view of a support structure suitable for usein connection with the apparatus of FIG. 3, for holding the glass sheetduring the cutting process; and

FIG. 6 is a schematic side view of a more localized portion of thesupport structure and glass sheet, showing effects of support fluid, thevacuum fluid, and/or cooling fluid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings wherein like numerals indicate likeelements there is shown in FIG. 1 a top view of a thin, glass substrate10 produced using one or more cutting methodologies and apparatusdisclosed herein. A number of characteristics of the glass substrate 10are of importance when considering the disclosure herein. First, theglass substrate (and the source glass sheet from which it is cut) isthin and/or ultra-thin, with a thickness of less than about 0.3 mm, forexample between about 0.03 mm to 0.3 mm, and/or between about 0.05 mm to0.2 mm. While these thicknesses are considered preferable, andrepresentative of thicknesses not heretofore usable in connection withexisting free-form shape cutting techniques, the glass substrate 10 maybe thinner and/or thicker than the ranges mentioned. Second, the glasssubstrate 10 is considered a free form shape, for example having atleast one curved portion, and indeed potentially a plurality of curvedportions, having one or more radii of curvature anywhere from a minimumof about 2 mm up to infinity (which is a straight line). For example,the glass substrate 10 is shown with four rounded corners, although anyother shape may be employed, for example having a mix of roundedcorners, sharp corners, straight beveled corners, etc. Third, the glasssubstrate 10 is intended to be formed via a one step, full separationcutting methodology in which the desired shape is obtained from a thinsource glass sheet.

Reference is now made to FIG. 2, which is a top view of a source glasssheet 20 from which the glass substrate 10 of FIG. 1 may be produced.The novel methodology and apparatus disclosed herein provides forcutting the glass substrate 10 via propagation of a crack in the sourceglass sheet using a laser for example a CO2 laser beam) and simultaneousprovision of a cooling fluid (for example a gas, for example air). Ingeneral, this arrangement results in the controlled propagation of thecrack in the source glass sheet 20 along a desired cutting line in orderto separate the glass substrate 10 from the glass sheet 20. A moredetailed discussion of the methodology and apparatus for carrying outthe initiation, propagation, and termination of the crack is providedlater in this description.

As an initial phase of the process, the source glass sheet 20 (of theaforementioned thickness) is supported on a suitable support structure(which will be discussed in more detail later herein) and a free formcutting line (the dashed line in FIG. 2) is defined that establishes aclosed pattern, where the cutting line circumscribes the desired finalshape of the glass substrate 10.

As will be discussed in more detail later herein, there are a number ofoptions for the start of the cutting line and the finish of the cuttingline. For example, as illustrated in the encircled area of interest inFIG. 2, one option is that the start and finish 52 of the cutting lineare co-incident (see the left most illustration). In this firstconfiguration, the cutting line is entirely coincident with the desiredcontour of the glass substrate 10. Alternatively, the start 30 of thecutting line may be at a different point as compared to the finish 40 ofthe cutting line (see the right most illustration). In this secondconfiguration, at least a portion of the cutting line is not coincidentwith the desired contour of the glass substrate 10. The implications foreach option will be discussed later herein, however, at this point it issufficient to point out that various options for the start/finish of thecutting line exist.

An additional parameter that may be considered in connection withdefining the cutting line is the range of the waste width, W, i.e., thewidth of the waste material from the cutting line to the outer peripheryof the source glass sheet 20 (usually measured perpendicularly from thecutting line). It has been discovered that the waste width parameter mayhave an appreciable effect on the edge quality of the finished glasssubstrate 10, although the waste width W may be expressed as a rangeinstead of a particular single number.

As will be discussed in more detail later, the effect of the waste widthparameter arises in connection with the structure supporting the glasssheet 20 during the cutting process. As will be discussed later herein,the support structure may include an air bearing mechanism to provide anair flow (from below) to counter the force of gravity on the glass sheet20 in order to support (or float) the glass sheet 20. The air flow willalso act (again from below) upon the waste portion of the glass sheet20, represented by the waste width W. Notably, the waste portion may nothave any counter force from above other than the force of gravity, and asource of cooling fluid (which will be discussed in detail laterherein). In general, when the waste width W becomes too small, forexample, about 5 mm for the thin glass thicknesses being contemplated,the waste portion of the glass sheet 20 is relatively light and is moresusceptible to vibrations induced by air flows during the cuttingprocess. Indeed, vibrations of the waste portion of the glass sheet 20during cutting can lead to defect formation on the cut edge of the glasssubstrate 10. When the waste width W becomes too large, and the wasteportion of glass sheet 20 becomes relatively heavy, the weight preventsexpansion of the glass in the cutting zone during the cutting process,which may create an external compression force affecting propagation ofthe crack. It has been determined that the waste width, W, may varywithin relatively large range of about 5-50 mm, about 15-40 mm, and/orabout 20-25 mm (for about a 0.1 mm thick glass sheet 20)—withoutadversely impacting the edge quality of the cut glass substrate 10.

Another important parameter in connection with achieving suitable cutedge quality on the finished glass substrate 10 is the initiation of acrack over a small length on the glass sheet 20, which is subsequentlypicked up and propagated using the aforementioned laser cuttingtechnique. In general, the glass sheet 20 is scored at an initiationline (the initial crack) using a mechanical scoring device, for examplea score wheel. In order to appreciate the significance of the crackinitiation and subsequent propagation of the crack, a more detaileddiscussion of the laser cutting technique will first be provided.

The laser is used to heat the glass sheet 20 in a localized area andthen to rapidly cool that area in order to create transient tensilestress via the resultant temperature gradient. The aforementionedinitial crack (initiation line) is created by introducing a smallinitial flaw on the surface of the glass sheet 20, which is thentransformed into a vent (the crack) propagated by heating the localizedzone via the laser and cooling that zone via quenching action producedby the cooling fluid. The tensile stress, σ, produced during the processis proportional to α*E*ΔT, where α is a linear thermal expansioncoefficient of the glass sheet 20, E is a modulus of elasticity of theglass sheet 20, and ΔT is a temperature difference on the surface of theglass sheet 20 produced by the heating (from the laser) the cooling(from the fluid). The tensile stress is controlled in order to be higherthan the molecular bonds of the glass sheet 20. For a given α*E tensilestress, σ can be increased by heating the glass sheet 20 to a highertemperature via the laser. However, overheating the glass sheet 20(above its strain point) will cause an ablation and irreversible highresidual stress, which deteriorates the quality of the cut edge andreduces edge strength. The described method uses full body glassseparation (cutting), where the vent depth is equal to the thickness ofthe glass.

Returning now to the issue of the initiation of the crack over a smalllength (the initiation line) on the glass sheet 20, a mechanical tool (ascoring device), for example a cutting wheel, may be used to produce arelatively short crack of sufficient depth in the surface of the glasssheet 20. As illustrated in FIG. 2, the left-most illustration of theencircled area of interest shows that an initial crack 52 may be placedat the start of the cutting line, where the cutting line is entirely onthe desired contour of the desired glass substrate 10. Alternatively, asshown in the right-most illustration of the encircled area of interestshows that the initial crack 52 may be placed outside a perimeter of thedesired contour (i.e., outside the perimeter of the final glasssubstrate 10), again at the start 30 of the cutting line. For thereasons discussed immediately below, it may be desirable to employ thelatter approach to positioning the initial crack 52.

Indeed, an important issue to keep in mind concerning the location ofthe initiation of the crack 52 is that the mechanical damage to theglass sheet 20 by the mechanical action creates a defect or a short lineof defects, which remains among the weakest section(s) of the cut edgeof the glass substrate 10 after cutting. Another important issue is thatapplication of the laser to heat the glass sheet 20 and initiation ofseparation results in the initial propagation of the crack, whichbecomes stable only after a certain distance from the initial crack 52.The length of the unstable section of the crack (and thus undesirableedge characteristics) varies depending on many factors, for example asize of the mechanical defect, the laser beam size, the laser power, thethickness of the glass sheet 20, etc. When a score and mechanical breakprocess is used for cutting, the defect initiation sections are simplycut-off and left as glass waste. Thus, it is desirable to minimize thesize of the unstable section of the crack (which cannot be removed) inorder to reduce imperfections in the cut edge. One way to minimize thesize of the unstable section of the crack is to employ a laser beam ofcertain characteristics, which will be discussed later herein.

Reference is now made to FIG. 2 and FIG. 3, the latter figure being aschematic illustration of an apparatus 100 that may be used to cut theglass substrate 10 from the glass sheet 20. The glass sheet 20 may besupported using a support structure 102 (which will be described ingreater detail later herein). The laser beam 60 may be implemented usinga source 64 of laser energy, folding optics 66, and focusing optics 68.Application of the laser beam 60 to the glass sheet 20 starting at theinitiation line (the initial crack) initiates propagation of the crack.Continuous moving of the laser beam 60 relative to the glass sheet 20along the cutting line elevates the temperature of the glass sheet 20 atthe cutting line (preferably to a substantially consistent temperature).Simultaneously, the cooling fluid 62 is applied relative to the laserbeam 60 (via a nozzle 70), such that the cooling fluid 62 causes atemperature differential in the glass sheet 20 in order to induce theaforementioned tensile stress and propagate the crack (i.e., a fractureor vent) in the glass sheet 20 along the cutting line. Movement of thelaser beam 60 and nozzle 70 relative to the glass sheet 20 may beachieved through any of the known conveyance mechanisms.

Another important parameter in connection with achieving satisfactorycut edge quality on the finished glass substrate 10 is termination ofthe propagation of the crack, for example in the vicinity of aperipheral edge of the glass substrate 10, which may be seen at thefinish 40 of the cutting line in FIG. 2 (right most illustration). Whenthe laser beam 60 approaches the edge of the glass substrate 10, aleading edge of the laser beam 60 moves off the glass substrate 10, andtherefore a portion of the energy of the laser beam 60 (i.e., in theleading section of the laser beam 60) does not contribute to maintainingthe tensile stress required for stable crack propagation. The closer thelaser beam 60 moves to the edge of the glass substrate 10, the more beamenergy is lost. As a result, the crack propagation originally driven bythe laser beam 60 stops and does not reach the edge of the glasssubstrate 10. Typically, the last section of the glass that fails toseparate through crack propagation is completed by external forces, forexample manual glass bending or pulling, which are usually not alignedwith the original crack propagation direction, thereby causing a “hook”at the end of the cut. The length of the hook varies depending on anumber of factors, is very undesirable, and therefore should beminimized in order to obtain satisfactory cut edge quality.

These two issues (crack initiation and crack termination) are addressedthrough a number of factors. First, it has been found that a particularcombination of laser beam size, laser beam shape, and cooling fluiddelivery affects the crack initiation, propagation, and termination infavorable ways. To appreciate the contemplated combination, a briefdiscussion of a traditional laser beam configuration is provided. Inparticular, the traditional configuration includes an elongated laserbeam of various dimensions followed by the cooling fluid—where thesource of the cooling fluid is positioned in an offset linearrelationship (a trailing configuration) with respect to the elongatelaser beam. This traditional arrangement (elongate laser beam andtrailing coolant) is very efficient for straight laser cutting (orscoring), however, it does not allow for changing the direction of thecrack propagation—and therefore no curved crack propagation is possible.

Turning again to FIGS. 2 and 3, it has been discovered that curved, freeform laser cutting may be achieved using a laser beam 60 of a roundshape surrounded by an annular, circular, ring-shaped coolant zone 62(achieved using the coolant source nozzle 70). The circular laser beam60, together with the annular coolant zone 62 does not exhibit anypredefined or inherent orientation, and therefore can be used topropagate the crack in any direction (without having to use any complexbeam shaping techniques or provide any additional motion axes formovement of the nozzle 70). While nozzles that produce annular,ring-shaped fluid flow in laser cutting applications are known, theyhave heretofore been applied to straight laser cutting methodologies orto cutting thicker glass via the score and break method (where a partialvent is created followed by mechanical break). In contrast, theembodiments herein employ a ring nozzle 70 for a full body separation(or cut) of a thin glass sheet 20. Additionally, while small diameterlaser beams are also known for free form laser cutting, the embodimentsherein apply a combination of the nozzle 70 for annular fluid flow (instationary relationship to the laser beam 60), where the fluid flow isvariable to achieve a variable annular coolant pattern, and of a smallround laser beam 60. The diameter of the laser beam 60 is about 1-4 mm,preferably about 2 mm, with a Gaussian or flat-top beam powerdistribution.

The source of laser power 64 may be implemented using CO2 lasermechanisms, however, other implementations are possible, for example afiber laser, an Nd:YAG laser, or other laser systems. A carbon dioxidelaser operates at the wavelength of 10.6 μm. In general, using a laserbeam 60 having the diameters disclosed herein allows certainadvantageous effects: (i) minimization of edge imperfections associatedwith the crack initiation (the smaller the beam diameter, the smallerthe unstable crack propagation zone); (ii) ability to propagate thecrack nearly to the edge of the glass sheet 20 (i.e., to permittermination of the crack in proximity to the edge of the glass sheet 20,thereby avoiding a hook at the end of the cut; and (iii) maintainingreasonably high cutting speed even with a small diameter beam, resultingin relatively short processing time and high throughput.

Referring to FIG. 2, as noted above, the initial crack (or initial line)may be applied to the surface of the glass sheet 20 along the cuttingline at the start/finish thereof (see left-most illustration). It hasbeen found, however, that better edge quality and strength of the glasssubstrate 10 may be achieved by placing the initial crack 52 at alocation outside the cutting line and outside the closed pattern thatcircumscribes the desired final shape (see right-most illustration). Inthe illustrated example, the resulting shape of the glass substrate 10may be a sharp corner since the cutting line crosses itself at thecorner.

In an alternative embodiment, a termination line 54 may be applied tothe surface of the glass sheet 20, for example by way of scoring or thelike. The termination line 54 is applied in such a way as to cross thecutting line transversely at at least one place, for example the twoplaces shown in the right-most illustration of FIG. 2. The terminationline 54 may be used as a site for a score and snap technique to producea straight chamfer at the corner of the glass substrate 10. Notably, thescore and snap along the termination line 54 eliminates anyimperfections from the crack initiation area 52 and the termination 40.Thus, this embodiment may be summarized as follows (in order): (i)mechanical scoring of the glass sheet 20 to apply the termination line54 (for a chamfered corner), (ii) mechanical initiation (e.g., scoring)of the initial crack 52 at the start 30 at the edge of the glass sheetoutside the closed pattern that circumscribes the desired final shape,(iii) application of laser beam 60 and cooling fluid 62 (continuously)for full body separation at the start 30 and at the site of the initialcrack 52, extending along the cutting line outside the closed pattern,crossing the termination line 54 at a first location, continuing alongthe cutting line on the closed pattern, crossing the termination line 54at a second location, continuing along the cutting line outside theclosed pattern, and terminating at the finish 40, (iv) removing theglass waste and extracting the glass substrate 10, and (v) applying amechanical (manual) break of chamfered corner (or corners if more thanone termination line 54 is applied at various locations).

Another important parameter in connection with achieving satisfactorycut edge quality on the finished glass substrate 10 is controlling thetemperature at the surface of the glass sheet 20 as the laser beam 60(and the nozzle 70) move relative to the cutting line. It has beendiscovered that a substantially constant temperature is desirable;however, once a desired temperature is established, one must take stepsto ensure such temperature may be controlled whilst the laser beam 60 istraversing a non-straight cutting line. Indeed, while the edge qualityof a straight cut may be better when the cutting speed is relativelyhigh, propagating the crack through arched regions (for example cornersand the like), especially sections of small radii, requires a reductionof the cutting speed (i.e., a reduction in the relative speed of thelaser beam 60 versus the cutting line). In order to ensure a relativelyconstant temperature through curved sections of the cutting line (i.e.,where the relative speed of the laser beam 60 changes), the power of thelaser beam 60 should be likewise changed (i.e., a reduction in powershould accompany a reduction in speed). The controlled relationshipbetween speed and power of the laser beam 60 relative to the cuttingline should be maintained in order to ensure the constant temperature ofthe glass surface and resultant constant stress field induced by theheating/cooling.

Reference is now made to FIG. 4, which is a graphical representation ofspeed and power curves suitable for use in connection with employing theapparatus of FIG. 3 to cut the glass substrate 10 from the glass sheet20. In the illustrated figure, the upper plot represents the speed ofthe laser beam 60 relative to the cutting line (e.g., in meters perminute) along the Y-axis and time (or distance from the starting point)along the X-axis. The lower plot represents the power of the laser beam60 along the Y-axis and time (or distance from the starting point) alongthe X-axis. As noted above, higher laser beam translation speeds requirehigher laser power in order to maintain the required consistenttemperature and stress, while lower beam translation speeds requirelower laser power to maintain the required consistent temperature andstress. The plots of FIG. 4 illustrate suitable profiles for cutting theglass sheet 20 of FIG. 2, namely a rectangular shape with three roundcorners. The desired temperature (and therefore the cutting speed andlaser power profiles) depends on a few factors, for example the laserbeam diameter, the glass thickness, and other glass properties. As anexample, a typical cutting speed for a glass sheet 20 formed fromCorning® Eagle XG® glass (of 0.1 mm thickness) may be in the range ofabout 1-2 m/min for a straight cut, and about 0.2-0.4 m/min for cornercuts of about 2 mm radius. Larger corner radii will allow for fasterspeeds. The Laser power required to cut the glass sheet 20 of CorningEagle XG glass may be about 5-15 W (which is a relatively low powerlevel for a CO2 laser apparatus). As illustrated, the straight sections(e.g., 200) exhibit higher speed and power, while the curved sections(e.g., 202) exhibit lower speed and power.

Another important set of parameters in connection with achievingsatisfactory cut edge quality on the finished glass substrate 10 isproviding the functions of transporting the glass sheet 20 (into and outof the cutting zone of the apparatus 100) and holding the glass sheet 20during the cutting process. In this regard, reference is made to FIG. 5,which is a schematic side view of an implementation of the supportstructure 102 of the apparatus 100 of FIG. 3. Assuming that the supportstructure 102 will be used for transportation, scoring, and lasercutting (which is a desirable combination), then the surface propertiesof the support structure 102 (especially the surface underneath theglass sheet 20), and the mechanisms contributing to the support of theglass sheet 20 during cutting are very important for cutting thinflexible glass of the thicknesses contemplated herein.

As for the mechanical scoring of the glass sheet 20 used for crackinitiation and for creation of termination lines, the hardness of thesurface of the support structure 102 under the glass sheet 20 is animportant factor. Indeed, if the surface is too soft, then the glasssheet 20 will flex under the pressure from the scoring mechanism (e.g.,the score wheel), which reduces and causes fluctuations in the forcegenerated by the scoring mechanism and leads to inconsistent crackpropagation and non-uniform initial crack depth. Thus, for therelatively thin glass sheet 20 it is preferred to have relatively hardsurface supporting the glass sheet 20 during scoring, thereby reducingglass flexure and providing constant and repeatable force from thescoring mechanism. Again, assuming that the same support structure 102is to be used to carry out the mechanical scoring processes and thelaser cutting process (e.g., with a CO2 laser mechanism), then thesurface of the support structure 102 should be able to withstandrelatively high temperatures generated by the laser beam 60. Given theserequirements, aluminum and/or stainless steel should be used toimplement the surface of the support structure 102 under the glass sheet20.

In order to move the glass sheet 20 into position for mechanical scoringand laser cutting, and then to move the glass substrate 10 (after thecutting process is complete) an air bearing mechanism is provided in thesupport structure 102. In addition, during the laser cutting process theglass sheet 20 must be held in position. Although commercially availablepressure/vacuum tables with discrete air and vacuum holes are available,they are only suitable for glass with standard thicknesses (e.g., atleast about 0.4 mm). In the case of the thin (or ultra-thin) flexibleglass sheet 20 herein, the discrete air and vacuum ports in acommercially available pressure/vacuum table causes localizeddeformation of, and stress in, the glass sheet 20, which significantlydisturb the mechanical scoring and laser cutting processes, often makingsatisfactory cutting impossible when the cutting line is close to one ofthe ports, or affecting edge quality, edge strength and/or edgegeometry. Accordingly, the support structure 102 contemplated herein isnot a common, commercially available pressure/vacuum table. Instead, aporous surface of the support structure 102 is preferably of an aluminumand/or stainless steel material, where the table provides: (i) anair-bearing mode for transportation of the glass sheet 20 (and the glasssubstrate 10), (ii) a vacuum mode (over the entire table) for holdingthe glass sheet 20 (e.g., during scoring), and (iii) an air-bearing modecombined with vacuum mode during laser cutting, whereby localized vacuummay be applied selectively through a pattern of vacuum zones, wherevacuum is provided through the porous surface.

The air bearing mode is characterized by applying support fluid to oneor more respective portions of the glass sheet 20 at least in proximityto the cutting line but preferable over a much larger area, and from aside (the underside) of the glass sheet 20 opposite to the cooling fluid62 and the laser beam 60. The support fluid of the air bearing isdelivered from the surface of the support structure 102 by way of theporosity of the surface and a source of fluid of varying pressure andflow (not shown). The air bearing mode operates to bias the glass sheet20 away from the surface of the table of the support structure 20 as thelaser beam 60 elevates the temperature of the glass sheet 20 and thecooling fluid 62 is directed in opposing fashion to the support fluid.

As illustrated in FIGS. 2 and 5, the vacuum mode provides for discretevacuum zones 110 (only a few zones being shown for purposes of clarity),not discrete holes but areas of various dimensions and shapes (forexample circular, rectangular, etc.). The vacuum zones 110 are bestlocated within the closed pattern of the cutting line that circumscribesthe desired final shape, such that they apply negative fluid pressureand negative fluid flow to the glass sheet 20, and bias and hold theglass sheet 20 toward the surface of the support structure 102 duringapplication of the laser beam 60. A size of a circular vacuum zone 110(as illustrated) may be 5-25 mm in diameter, however, differentdimensions are possible depending on size and shape of the glasssubstrate 10. The number and location of the discrete vacuum zones 110also depends on the size and shape of the glass sheet 20. The number ofvacuum zones 110 will depend on the size of the zones 110 versus thesize of the glass sheet 20. For relatively small vacuum zones, at leasttwo vacuum zones may be needed to hold the glass sheet 20 and avoidtranslational movement and/or rotation during the cutting process.Alternatively, one or two larger vacuum zones 110A may be sufficient toprovide the requisite holding function.

It is noted that the vacuum zones 110 will have an effect on the lasercutting process and the resultant edge characteristics of the glasssubstrate 10 because stress will be induced in the glass sheet 20 aroundthe vacuum zones 110. For example, as shown in FIG. 5, the vacuum zones110 tend to bias certain areas of the glass sheet 20 (in the vicinity ofthe zones 110) toward the surface of the support structure 102. In orderto address the effect of the vacuum zones 110, one may be sure that thecutting line is located at a minimum distance D (see FIG. 2) from theborders of the vacuum zones 110. As an example, a safe minimum distanceD may be about 25-50 mm for a glass thickness of about 0.1 mm.

Reference is now made to FIG. 6, which illustrates a localized side viewof the effects of the combined air bearing and vacuum mode. This modeapplies the support fluid (flow and positive pressure), the vacuum fluid(flow and negative pressure), and/or the cooling fluid (flow andopposing positive pressure) in order to provide a balanced mechanicalsupport and localized orientation of the glass sheet 20 duringpropagation of the crack by the laser beam 60 and cooling fluid 62.Indeed, some or all of these sources of fluid flow may interact in sucha way as to effect global and localized influences on the deformation ofthe glass sheet 20. As shown in FIG. 6, the interaction of the supportfluid from beneath the glass sheet 20 and the cooling fluid from abovethe glass sheet 20, if balanced, may provide for a depression zone 120(a mechanical deformation) around the laser beam 60, which forms astress field around the cut. The stress field assists in stabilizingpropagation of the crack.

Notably, while the cooling fluid is primarily provided for inducing athermal differential in the glass sheet 20 (in opposition to the heatprovided by the laser beam 60), the cooling fluid also provides amechanical function contributing to the depression zone 120 (andresultant stress field) in the glass sheet 20. Similarly, although theprimary function of the support fluid is to provide a mechanicalfunction (in opposition to the force of gravity on the glass sheet 20),the support fluid also provides a thermal function contributing to thethermal differential in the glass sheet 20 (in opposition to the heatprovided by the laser beam 60).

The speed and power of the laser depend on the thermal conditions of thebottom surface of the glass sheet 20, which is effected by the coolingthat is at least partially provided by the support fluid. In addition,there is variability in heat dissipation from the bottom surface of theglass sheet 20 into the surface of the support structure 102 thatdepends on the float gap between the bottom surface of the glass sheet20 and the surface of the support structure 102. The dissipation ismaximized when the float gap is zero, i.e., when there is contact of theglass sheet 20 to the surface of the support structure 102. The floatgap is primarily controlled by the support fluid, but the gap is alsoaffected by the influence of the cooling fluid bearing down on the glasssheet 20 from above. Thus, higher laser power and/or lower speed mightbe required as the gap reduces, while lower laser power and/or higherspeed might be required as the gap increases.

When the interrelationships between the support fluid, the coolingfluid, the laser power, and the laser speed are balanced, the depressionzone 120 (and stress field), the gap, and the cooling effects of thefluids around the cut assist in stabilizing propagation of the crack andimproving the edge characteristics of the finished glass substrate 10.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of theembodiments herein. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present application. Example arrangements are set forth in thefollowing aspects.

According to a first aspect, there is provided a method, comprising:

supporting a source glass sheet and defining an at least partiallynon-straight cutting line that establishes a closed pattern thatcircumscribes a desired final shape, where the glass sheet is 0.3 mm orless in thickness;

scoring the glass sheet at an initiation line using a mechanical scoringdevice;

applying a laser beam to the glass sheet starting at the initiation lineand continuously moving the laser beam relative to the glass sheet alongthe cutting line to elevate a temperature of the glass sheet at thecutting line to a substantially consistent temperature, where the laserbeam is of a circular shape;

applying a cooling fluid simultaneously with the application of thelaser beam, such that the cooling fluid at least reduces the temperatureof the glass sheet in order to propagate a fracture in the glass sheetalong the cutting line; and

separating waste glass from the glass sheet from the desired shape.

According to a second aspect, there if provided the method of aspect 1,wherein a diameter of the laser beam is one of: (i) between about 1 mmto about 4 mm, and (ii) 2 mm.

According to a third aspect, there is provided the method of aspect 1 oraspect 2, wherein one of: (i) the initiation line is applied on andalong a portion of the cutting line; and (ii) the initiation line isapplied to the glass sheet at a location outside the cutting line andoutside the closed pattern that circumscribes the desired final shape.

According to a fourth aspect, there is provided the method of any one ofaspects 1-3, further comprising scoring a termination line into theglass, where the termination line crosses the cutting line transverselyat one of: (i) one place, and (ii) two places.

According to a fifth aspect, there is provided the method of aspect 4,wherein the termination line crosses the cutting line in two places andis a portion of the cutting line, resulting in the portion of cuttingline being for a chamfered corner of the final desired shape.

According to a sixth aspect, there is provided the method of any one ofaspects 1-5, further comprising varying a speed of the movement of thelaser beam relative to the glass sheet such that the speed is higherwhen the cutting line is straight as compared with when the cutting lineis curved.

According to a seventh aspect, there is provided the method of aspect 6,wherein at least one of: (i) the speed is between about 1-2 meters perminute when the cutting line is straight, and (ii) the speed is betweenabout 0.2-0.4 meters per minute when the cutting line is curved.

According to an eighth aspect, there is provided the method of aspect 6,further comprising varying a power level of the laser beam as a functionof the speed of the movement of the laser beam relative to the glasssheet such that the temperature of the glass sheet at the cutting lineis maintained at the substantially consistent temperature irrespectiveof whether the cutting line is straight or whether the cutting line iscurved.

According to a ninth aspect, there is provided the method of any one ofaspects 1-8, further comprising:

applying one or more vacuum zones within the closed pattern thatcircumscribes the desired final shape to apply negative fluid pressureand negative fluid flow to the glass sheet and to bias and hold theglass sheet to a support table during application of the laser beam; and

applying support fluid to one or more respective portions of the glasssheet in proximity to the cutting line, and from a side of the glasssheet opposite to the cooling fluid and the laser beam, to bias theglass sheet away from the table as the laser beam elevates thetemperature of the glass.

According to a tenth aspect, there is provided the method of aspect 9,wherein each vacuum zone is a minimum of about 5 mm-25 mm in diameter.

According to an eleventh aspect, there is provided the method of aspect9, further comprising controlling a fluid flow and pressure of thecooling fluid and a fluid flow and pressure of the support fluid toprovide a balanced mechanical support of the glass sheet and cooling ofthe glass sheet to propagate the fracture of the glass sheet along thecutting line.

According to a twelfth aspect, there is provided the method of aspect 9,wherein the one or more vacuum zones are at least about 25-50 mm awayfrom the cutting line.

According to a thirteenth aspect, there is provided the method of anyone of aspects 1-12, wherein respective perpendicular distances from thecutting line to a closest edge of the glass sheet is one of: (i) betweenabut 5-50 mm; (ii) between abut 15-40 mm; and (iii) between abut 20-25mm.

According to a fourteenth aspect, there is provided the method any oneof aspects 1-13, wherein the cooling fluid is directed annularly aboutthe laser beam toward the glass sheet.

According to a fifteenth aspect, there is provided an apparatus forcutting a glass sheet into a desired shape, comprising:

a support table operating to support the glass sheet, which is 0.3 mm orless, the glass sheet having a defined and at least partiallynon-straight cutting line that establishes a closed pattern thatcircumscribes the desired final shape;

a mechanical scoring device operating to score the glass sheet at aninitiation line;

a laser source operating to apply a laser beam to the glass sheetstarting at the initiation line and continuously moving the laser beamrelative to the glass sheet along the cutting line to elevate atemperature of the glass sheet at the cutting line to a substantiallyconsistent temperature, where the laser beam is of a circular shape;

a source of cooling fluid operating to apply a cooling fluidsimultaneously with the application of the laser beam, such that thecooling fluid at least reduces the temperature of the glass sheet inorder to propagate a fracture in the glass sheet along the cutting linesuch that waste glass may be separated from the glass sheet to result inthe desired shape.

According to a sixteenth aspect, there is provided the apparatus ofaspect 15, wherein a diameter of the laser beam is one of: (i) betweenabout 1 mm to about 4 mm, and (ii) 2 mm.

According to a seventeenth aspect, there is provided the apparatus ofaspect 15 or aspect 16, further comprising: a conveying device operatingto vary a speed of the movement of the laser beam relative to the glasssheet such that the speed is higher when the cutting line is straight ascompared with when the cutting line is curved.

According to an eighteenth aspect, there is provided the apparatus ofany one of aspects 15-17, further comprising a power supply deviceoperating to vary a power level of the laser beam as a function of thespeed of the movement of the laser beam relative to the glass sheet suchthat the temperature of the glass sheet at the cutting line ismaintained at the substantially consistent temperature irrespective ofwhether the cutting line is straight or whether the cutting line iscurved.

According to a nineteenth aspect, there is provided the apparatus of anyone of aspects 15-18, wherein the support table includes:

one or more vacuum zones, located within the closed pattern thatcircumscribes the desired final shape, operating to apply negative fluidpressure and negative fluid flow to the glass sheet and to bias and holdthe glass sheet to the support table during application of the laserbeam; and

one or more sources of support fluid operating to apply the supportfluid to one or more respective portions of the glass sheet in proximityto the cutting line, and from a side of the glass sheet opposite to thecooling fluid and the laser beam, to bias the glass sheet away from thetable as the laser beam elevates the temperature of the glass,

wherein a fluid flow and pressure of the cooling fluid and a fluid flowand pressure of the support fluid are controlled to provide a balancedmechanical support of the glass sheet and cooling of the glass sheet topropagate the fracture of the glass sheet along the cutting line.

According to a twentieth aspect, there is provided the apparatus of anyone of aspects 15-19, wherein the cooling fluid is directed annularlyabout the laser beam toward the glass sheet.

According to a twenty first aspect, there is provided the apparatus ofany one of aspects 15-20, wherein the cutting line is a minimum wastewidth, W, away from an outer periphery of the glass sheet, measuredperpendicularly from the cutting line.

1-14. (canceled)
 15. An apparatus for cutting a glass sheet into adesired shape, comprising: a support table operating to support theglass sheet, which is 0.3 mm or less, the glass sheet having a definedand at least partially non-straight cutting line that establishes aclosed pattern that circumscribes the desired final shape; a mechanicalscoring device operating to score the glass sheet at an initiation line;a laser source operating to apply a laser beam to the glass sheetstarting at the initiation line and continuously moving the laser beamrelative to the glass sheet along the cutting line to elevate atemperature of the glass sheet at the cutting line to a substantiallyconsistent temperature, where the laser beam is of a circular shape; asource of cooling fluid operating to apply a cooling fluidsimultaneously with the application of the laser beam, such that thecooling fluid at least reduces the temperature of the glass sheet inorder to propagate a fracture in the glass sheet along the cutting linesuch that waste glass may be separated from the glass sheet to result inthe desired shape.
 16. The apparatus of claim 15, wherein a diameter ofthe laser beam is one of: (i) between about 1 mm to about 4 mm, and (ii)2 mm.
 17. The apparatus of claim 15, further comprising: a conveyingdevice operating to vary a speed of the movement of the laser beamrelative to the glass sheet such that the speed is higher when thecutting line is straight as compared with when the cutting line iscurved.
 18. The apparatus of claim 15, further comprising a power supplydevice operating to vary a power level of the laser beam as a functionof the speed of the movement of the laser beam relative to the glasssheet such that the temperature of the glass sheet at the cutting lineis maintained at the substantially consistent temperature irrespectiveof whether the cutting line is straight or whether the cutting line iscurved.
 19. The apparatus of claim 15, wherein the support tableincludes: one or more vacuum zones, located within the closed patternthat circumscribes the desired final shape, operating to apply negativefluid pressure and negative fluid flow to the glass sheet and to biasand hold the glass sheet to the support table during application of thelaser beam; and one or more sources of support fluid operating to applythe support fluid to one or more respective portions of the glass sheetin proximity to the cutting line, and from a side of the glass sheetopposite to the cooling fluid and the laser beam, to bias the glasssheet away from the table as the laser beam elevates the temperature ofthe glass, wherein a fluid flow and pressure of the cooling fluid and afluid flow and pressure of the support fluid are controlled to provide abalanced mechanical support of the glass sheet and cooling of the glasssheet to propagate the fracture of the glass sheet along the cuttingline.
 20. The apparatus of claim 15, wherein the cooling fluid isdirected annularly about the laser beam toward the glass sheet.
 21. Theapparatus of claim 15, wherein the cutting line is a minimum wastewidth, W, away from an outer periphery of the glass sheet, measuredperpendicularly from the cutting line.